Because the same frequency band is used commonly by neighboring cells in a CDMA cellular mobile communication system, the practical capacity of a certain cell (the ability of a radio load of the cell) will be varied due to the strength variation of the interference of the neighboring cells. Particularly, under multi-traffic condition, because the burst feature of data traffic, the interference from the neighboring cells will cause the practical load ability of the present cell to change severely. Under a condition that the interference strength of the neighboring cells changes randomly, it is desired to accurately monitor the present load condition of the cells and predict the variation of the loads of the cells after receiving a new traffic so as to sufficiently utilize radio resources and ensure the quality of communication.
Monitoring system load of a CDMA system and analyzing capacity of a CDMA system are both closely related to interference power (or transmission power). However, the following important distinctions exist between them:
1) The objectives are different: a system capacity analysis is to obtain the extreme value of capacity under some assumptions, while load monitoring is to obtain in real time the practical extreme value of the capacity of the system, the occupation amount of an extreme value of the capacity, and the residual amount of the extreme value of the capacity in the practical operating system; and
2) The methods for processing the parameters are different: the model used for a system capacity analysis has explicitly ideal characteristics; and selected system parameters, acceptance or rejection of the parameters, and the like, are more or less impractical; and the parameters selected for system load monitoring have to include two features: (1) they would reflect a current load condition of a system in real time; and (2) they are operable in a practical system.
Accordingly, due to the above distinctions, the idea, analysis model and interference processing method used for system capacity analysis cannot be used for load monitoring. It is desired that load monitoring has its own analysis idea, analysis model, interference processing method, and parameter selection method.
A radio load monitoring method for a CDMA mobile communication system disclosed in U.S. Pat. No. 5,687,171 monitors load from an aspect of a granted access control. The method includes the following steps:
1) Measuring interference strength received by a base station;
2) Subtracting the measured interference strength from permitted total interference strength to obtain an interference tolerance value;
3) Calculating whether the interference produced after receiving new traffic exceeds the interference tolerance value obtained in step 2); and
4) Permitting access if the interference produced does not exceed the interference tolerance value; otherwise, rejecting access.
The above granted access method is based on load monitoring and prediction. However, the method does not address how to perform the load monitoring of multi-traffic and calculate interference produced after receiving new traffic.
The U.S. Pat. No. 6,005,852 and U.S. Pat. No. 5,790,534 submitted by Nokia disclosed a load control system which is composed of two parts of load control and load monitoring, in which a load control stratagem, such as granted access control, re-consultation of QoS, increasing of the delay of data traffics, and the like, is implemented in-real time (up to a measuring interval of 10 ms for providing the load condition of a cell, and a load control unit is based on an output of a load monitoring unit and incorporates the load condition of the neighboring cells) by the load monitoring for the load monitoring unit. The base station checks the current capacity (that is the actual capacity of the base station under interference condition, and the actual capacity can be indicated by traffic code rate and interference power) of the cell for each radio frame. Particularly, the permitted interference power of data traffics of the present cell is calculated by a load monitoring unit according to a frame period. If the interference of circuit traffics or the interference of neighboring cells changes, packet traffic load of a present cell is adjusted.
However, the above system does not implement the prediction under multi-traffic and lacks specific schemes of a load monitoring method for distinguishing traffics having different priorities.
The objective of the present invention is to provide an apparatus and method for implementing multi-traffic load monitoring and prediction in a CDMA cellular mobile communication system to monitor in real time the loads of different traffic types or the loads of the same traffic type having different priorities, to predict in real time the load of newly received traffic, to utilize radio resources sufficiently, to ensure system stability, and to improve quality of communication.